Monitoring of ground water quality is an effort to obtain information on chemical quality and its variation through representative samples.

The existing chemical quality data of the aquifers in the project areas is compiled by CGWB. In addition to regular groundwater sampling during groundwater level measurement at the National Ground water Monitoring Stations, an aquifer specific groundwater quality sampling network is developed. Collected samples are analysed in CGWB and other chemical laboratories. In addition to normal chemical constituents, information on the heavy metals and organic compounds in ground water is also generated. This leads to the preparation of aquifer water quality maps. Besides, specific studies are launched on geogenic contaminations like arsenic and fluoride in selected project areas.

Groundwater is in general of good quality in the pilot project areas. However, there are occurrences of saline groundwater in the desert of Jaisalmer district, Rajasthan, in Dausa district, Rajasthan and in the coastal tract of Vellar basin, Cuddalore district, Tamil Nadu. Occurrences of arsenic contamination, in excess of the limits prescribed for drinking water use, are reported in the western part of the project area in Bihar. The other main geogenic contaminants are fluoride and iron. There are also anthropogenic contaminants, such as nitrates, phosphates, heavy metals, etc, in some places due to various human activities.